1. Field of the Invention
The invention relates to thermal insulation with at least one closed-off cavity which contains an insulating material.
2. Description of the Prior Art
Such thermal insulations find application in preventing heat losses, especially in power engineering. They are intended particularly for devices such as batteries of the alkali metal and chalcogen type which are usually surrounded by heat insulation in order to prevent the storage cells from cooling down particularly in the pauses of the operation.
Thermal insulation for such batteries is already known. This insulation is substantially formed by an evacuated cavity, within which metal foil is arranged. This metal foil is especially made of aluminum or alloy steel and arranged at a predetermined mutual spacing. The cavity is defined by metallic walls. In order to avoid buckling of these defining walls (due to the vacuum present), the cavity is equipped with additional braces. For this purpose, rod-shaped supports can be considered which are arranged in the interior of the cavity between defining walls which extend parallel to each other. Stiffening of the outer walls, of course, is also conceivable. In the case of cylindrical defining walls of the cavity, such bracings are not necessary. The above-mentioned support elements, especially the rod-shaped braces, cause an additional heat flow from the interior of the insulation toward the outside. Thereby, the low thermal conductivity achieved by the metallic foil is to a considerable extent lost again.